Drainage devices such as shunts and catheters, for example, commonly are used by medical professionals to drain fluid from a patient's body. In some situations, fluid may need to be drained from operative sites or from wounds. Fluid drainage also may be performed to treat medical conditions for which the fluid causes abnormal pressures, whereby the drainage relieves the abnormal pressure.
Glaucoma, for example, is a disease of the major optic nerve, the nerve responsible for receiving light from the retina and transmitting impulses to the brain to be perceived as an image. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of peripheral vision. If glaucoma is not diagnosed and treated, it can progress to loss of central vision and ultimately to blindness. Glaucoma usually is associated with elevated pressure in the eye. Generally, it is this elevated eye pressure that leads to loss of sight through progressive damage to the optic nerve. Thus, in the treatment of glaucoma the principal objective is the lowering of intraocular pressure in the eye.
Numerous therapies using ophthalmic shunts as ocular drainage devices have been developed for treating glaucoma. Use of the ophthalmic shunts decreases the intraocular pressure by promoting fluid flow of aqueous humor from the eye. Typically, ophthalmic shunts are made from a silicone material that provide a passageway or multiple conduits adapted for permitting the evacuation of aqueous humor from the eye. But it has been found that ophthalmic shunts made from silicone can promote fibroblast growth around the ophthalmic shunt and that the fibroblasts can either completely encapsulate the shunt or block the one or more passageways of the shunt to prevent fluid from being evacuated from the eye. And regardless of the choice of material for an ophthalmic shunt, the ophthalmic shunt must be both conformal and pliable to be suitable for the delicate procedure of draining ocular fluid.
Among the many types of drainage devices, the problem of fibroblast growth is not unique to ophthalmic shunts. Fibroblast growth also can adversely affect other types of drainage devices, such as hydrocephalus shunts, arteriovenous shunts, thoracic catheters, and central venous access devices. The adverse effect is quite similar in all examples. That is, in these examples the fibroblasts may prevent fluid flow or fluid evacuation from the drainage devices. Likewise, even drainage devices that are embolic and used with long-term indwelling catheters can clog or become occluded as a result of fibroblast growth.
Accordingly, there is a need in the art for drainage devices that are made from materials capable of inhibiting fibroblast proliferation, devices that are specially configured for their specific application, or devices comprising both fibroblast-inhibiting materials and special configurations, to inhibit or completely prevent fibroblast growth around or within the drainage device.